Electronic Throttle Control (ETC) power management is utilized to remedy certain conditions that may arise during a vehicle operation, such as an increased probability of an engine stall, RPM errors, and transitions between torque control modes. A vehicle controller identifies whether the conditions exist by requesting changes to engine torque. Engine torque can be increased or decreased depending on the condition identified by the vehicle controller. Traditionally, ETC power management has utilized two methods for generating a requested torque engine signal: idle speed torque control and accelerator pedal torque control. The vehicle controller achieves the requested engine torque by retarding spark or disabling fuel to one or more cylinders.
Idle speed torque control utilizes classical Proportional/Integral terms to calculate a requested engine torque that is required to maintain the desired engine speed. This control method is available at lower vehicle speeds with no accelerator pedal input. Desired engine speed is determined by a separate function based on engine load, ambient temperature, coolant temperature, engine run time, and other factors.
Accelerator pedal torque control is typically active when idle speed torque control is not available. A desired torque is calculated based on a current accelerator pedal position and engine speed. Changes in requested engine torque are rate-limited to prevent excessive variation.
Under certain engine conditions, torque control may adversely impact engine components and/or performance. The vehicle controller closely monitors engine conditions prior to and during ETC power management to avoid the adverse impact. For example, increasing torque at high engine speeds and temperatures may reduce the efficiency of the catalytic converter. One method of protecting the catalytic converter from excessive temperatures involves using a catalyst material with a higher temperature tolerance. These catalyst materials typically reduce the efficiency of the catalytic converter at lower temperatures, and are often more expensive.
Another problem involves engine stall during accelerator pedal torque control. Engine load conditions may vary during accelerator pedal torque control, which causes a disparity between desired torque and actual torque. One method for preventing engine stalls during heavy load conditions uses a stall prevention algorithm to increase engine torque. The algorithm allocates the full amount of torque available at the respective speed to prevent engine stall. Full allocation of torque at low speeds is inefficient and leads to reduced fuel economy and engine life.